Pictured is a system I “integrated” in Plant City, Florida. For this roof, there is enough surface area to put down almost 6000 watts of solar panels. Because the roof has little pitch, we were able to put modules on the East and West facing roofs with less than 10% loss in efficiency. However, in order to keep the overall system efficient, we used two inverters, having two sets of strings with different number of modules in series.
If you have a steel roof, with flat “pans” of at least 16 inches between the ridges, then you can put down flexible modules. These UniSolar modules come with adhesive backing, are lightweight, and add no wind loading.
UniSolar PVL modules installed on steel roof.